74 STUDIES OF ANIMAL TYPES 



Determine the direction of the blood flow by the move- 

 ments of the bodies (the corpuscles) floating in the 

 blood. ' t ] 



There are two kinds of corpuscles in the blood, the red 

 ones and the white, or colorless ones. What is the shape 

 of a red corpuscle? The red ones, for the most part, are 

 in the middle of the currents while the white ones are along 

 the edges of the streams. Note that the red ones change 

 shape sometimes when crowded or pressed. Do they 

 resume their original shapes? 



Make drawings of the two kinds of corpuscles. 



C. INTERNAL FEATURES. Examine the mouth and note 

 the number and arrangement of the teeth on the upper 

 jaw and the absence of teeth from the lower jaw. Look 

 on the roof of the mouth for a patch of teeth. 



Note the long fleshy tongue. Draw it forward and de- 

 termine how it is attached to the mouth. Note the sticky 

 saliva on the tongue. Probably the manner in which this 

 animal procures food has already been determined. If 

 not, try again, or get a toad and confine it in a box con- 

 taining some moist earth and feed it with flies, beetles, etc. 

 The toad obtains its food in a manner similar to that of the 

 frog, is much more at home in captivity, and can more 

 easily be observed. 



In the back part of the floor of the mouth note the glot- 

 tis, the slitlike opening to the windpipe. 



Push a bristle down the nostrils, to determine where they 

 enter the mouth. 



Make an opening in the tympanic membrane and push a 

 bristle through the cavity of the internal ear into the mouth. 

 The tube through which the bristle enters the mouth is the 

 Eustachian tube. 



